1. Field of the Invention
The present invention relates to a hearing aid device for a hearing-impaired listener.
2. Description of the Related Art
Hearing aids have been in use since the early 1900s. The main concept of the hearing aid is to amplify sounds so as to help a hearing-impaired listener to hear, and to make the sound amplification process generate almost no sound delay. Furthermore, if a hearing aid performs frequency processing, generally the processing reduces the sound frequency. For example, U.S. Pat. No. 6,577,739 “Apparatus and methods for proportional audio compression and frequency shifting” discloses a method of compressing a sound signal according to a specific proportion for being provided to a hearing-impaired listener with hearing loss in a specific frequency range. However, this technique involves compressing the overall sound; even though it can perform real-time output, the compression can result in serious sound distortion.
If frequency reduction is performed only on some high-frequency sounds, the distortion will be reduced. However, this technique involves a huge amount of computation, which may delay the output, and therefore it is often inappropriate for real-time speech processing. For example, the applicant filed U.S. patent application Ser. No. 13/064,645 (Taiwan Patent Application Serial No. 099141772), which discloses a method to reduce distortion; however, it still causes an output delay problem.
Therefore, there is a need to provide a hearing aid and a method of enhancing speech output in real time to reduce distortion of the sound output as well as to reduce the delay of the sound output caused by frequency processing or amplification, so as to mitigate and/or obviate the aforementioned problems.